The objective of this project is to study the biochemical interactions of kallikrein with its substrates and inhibitors, the role of high molecular weight (HMW) kininogen in plasma proteolysis, the interaction of the contract systems with platelets, and measurements of the kinin forming system in human disease and animal models. Accomplishments this year include study of the interaction of kallikrein with antithrombin III, investigation of the activation of factor VII by factor XII, delineation of the interrelationship of prekallikrein and HMW kininogen, characterization of the role of HMW kininogen in contact and fluid phase activation of prekallikrein and factor XI and investigation of the interaction of platelet inhibitors with contact factors. The kinin forming system has been investigated in patients with septicemia, carcinoid and dumpingo syndrome. A patient with HMW kininogen has been studied. The relationship of bradykinin to angiotensin in low salt and high salt states has been studied. The kinin system has been investigated in women with oral contraceptives. Kallikrein and its inhibitors have been measured in a primate model of renal hyperacute rejection.